1. Field of the Invention
The present invention relates to an interface (electroencephalogram interface) system with which it is possible to manipulate a device by utilizing an electroencephalogram. More specifically, the present invention relates to an electroencephalogram interface system having a function of efficiently selecting an option which is desired by a user, from among a large number of options.
2. Description of the Related Art
In recent years, various types of information devices such as television sets, mobile phones, and PDAs (Personal Digital Assistants) have become prevalent, and thus a user needs to manipulate information devices in many scenes of usual life. Usually, as the manipulation inputting means thereof, methods such as pressing a button, moving a cursor and making a confirmation, and manipulating a mouse while watching a screen are used.
However, when both hands are unavailable due to tasks other than device manipulations, e.g., household chores, rearing of children, and driving an automobile, it is difficult to make an input by using the manipulation inputting means, so that a device manipulation cannot be realized. Therefore, there is an increasing needs of users to manipulate information devices in all situations.
Against such needs, an input means utilizing a biological signal from a user, or more specifically, an electroencephalogram interface which utilizes an event-related potential of an electroencephalogram of a user, has been developed. As used herein, an “event-related potential” refers to a transient potential fluctuation in the brain which occurs in temporal relationship with an external or internal event. An electroencephalogram interface utilizes an event-related potential which is measured since the timing of occurrence of an external event as a starting point. For example, it is supposedly possible to select a menu option by utilizing a component called P300 of an event-related potential which occurs in response to a visual stimulation or the like. The “P300” refers to a positive component of the event-related potential which appears around 300 milliseconds since the starting point.
Japanese Laid-Open Patent Publication No. 2005-discloses an electroencephalogram interface technique which uses an event-related potential to distinguish an option that a user wishes to select. To specifically explain the technique which is described in Japanese Laid-Open Patent Publication No. 2005-34620, options are randomly highlighted at a constant time interval, and the waveform of an event-related potential which appears about 300 milliseconds after the timing of highlighting an option as a starting point is utilized, thereby realizing distinction of an option which the user wishes to select. According to this technique, even in a situation where both hands are full, or even in a situation where the user is unable to move his or her limbs due to an illness or the like, the user can select an option which they wish to select. Thus, an interface for device manipulations, etc., that meets the aforementioned needs is realized.
In order to allow an event-related potential to be used for an interface, visual stimulations are necessary, e.g., allowing an option to be highlighted or popped up on an interface screen. In the case where there are many options (e.g., ten and a few, or several dozens), too much time will be required if each is individually highlighted, and therefore it is important to highlight them efficiently.
FIG. 18 shows an interface screen which is described in “The Mental Prosthesis: Assessing the Speed of a P300-Based Brain-Computer Interface”, Emanuel Donchin and two others, IEEE TRANSACTIONS ON REHABILITATION ENGINEERING, Vol. 8, No. 2, June, 2000 (hereinafter, Non-Patent Document 1). Thirty-six text characters are displayed in a 6×6 matrix. In Non-Patent Document 1, each row and each column are randomly highlighted at a constant time interval, and by utilizing the aforementioned event-related potential, it is distinguished at which row and which column the user is wishing to select a text character. As a result, the number of highlighting is reduced to 6+6=12 times, as opposed to 36 times which would have been required to individually highlight each.
On the other hand, a line-of-sight inputting interface technique employing a line-of-sight detection device has conventionally been proposed, as illustrated in Japanese Laid-Open Patent Publication No. 10-187334, for example. In Japanese Laid-Open Patent Publication No. 10-187334, a fixation region of a user on an interface screen is detected, and an option which is in the fixation region is regarded as being in a selected state. Then, when an option in a selected state exists, if the user's motion of closing an eyelid for a sufficiently long time (eyelid closure motion) is detected, it is determined that the selection of the option is finalized. As a result, a signal finalizing an inputting of information is output, whereby the selection is finalized.
According to this technique, if a threshold value of the time for detecting an eyelid closure motion of the user is set to a small value, for example, even an unconsciously performed blink will be incorrectly detected as the selection of an option being finalized, thus leading to a possibility that an inputting of information not intended by the user may occur. On the other hand, if the threshold value of the time for detecting an eyelid closure motion of the user is set to a large value, the possibility of incorrect detections related to blinks will be reduced, but the user will need to consciously maintain an eyelid closure motion for a long time, such that muscles around the eye may be fatigued due to too much strain.
As described above, a line-of-sight inputting interface compels a user to undergo a predetermined motion when finalizing the selection/execution of an option, whereas an electroencephalogram interface is very effective because of being able to distinguish an option that a user is wishing to select without compelling the user to undergo any predetermined motion.
In the above-described electroencephalogram interface technique, the options to be highlighted, the timing of beginning highlighting, and the time interval of highlighting are all uniquely determined by the interface system. Therefore, a user utilizing an electroencephalogram interface needs to wait for the desired option to be highlighted, and needs to keep his or her gaze fixed at the interface screen even while undesired options are highlighted. Therefore, options cannot always be selected efficiently.
As a result, the following problems have occurred.
A first example is that, even if the coordinate position of an option which is displayed on an electroencephalogram interface is clear, the user cannot quickly select an option of interest. In the case of the 6×6 options in Non-Patent Document 1 as described above, assuming that the highlighting interval is 350 milliseconds, as much time as 4.2 seconds (=350 milliseconds×12 times) will be required for one selection. This is a long time which would result in a feeling of inconvenience or frustration when a manipulation of a device to be used daily is contemplated.
A second example is that a user who is unclear and undecided as to what to select cannot smoothly make up his or her mind. The reason is that, when a large number of options are highlighted to a user who is unclear as to what to select, such highlighting will be unnecessary and disturbing to the user. When implementing an electroencephalogram interface in a daily application, the expected functions need to be exhibited without allowing the user to feel inconvenience or frustration.
An objective of the present invention is to, in a system having an interface which utilizes an electroencephalogram, allow a user wishing to select an option whose displayed position on an electroencephalogram interface is clear, or a user who is unclear as to which option should be selected, to efficiently select the option that is desired by the user from among a large number of options, without feeling inconvenience or frustration concerning the system.